Ion implantation is a process of depositing chemical species into a substrate by direct bombardment of the substrate with energized ions. In semiconductor manufacturing, ion implanters are used primarily for doping processes that alter a type and level of conductivity of target materials. A precise doping profile in an integrated circuit (IC) substrate and its thin-film structure is often crucial for proper IC performance. To achieve a desired doping profile, one or more ion species may be implanted in different doses and at different energy levels.
Moreover, ion implantation is currently the most common technique for introducing conductivity-altering impurities into semiconductor wafers. During such ion implantation, a desired impurity material is ionized in an ion source, generated ions are accelerated to form an ion beam of a prescribed energy, and the ion beam is directed at a surface of a semiconductor wafer. Energetic ions in the ion beam penetrate into semiconductor material in the semiconductor wafer and are embedded into a crystalline lattice of the semiconductor material to form a region of desired conductivity.
In the ion source, a gas or a solid material is typically converted into the ion beam. The ion beam is typically mass analyzed to eliminate undesired ion species, accelerated to a desired energy, and directed at the semiconductor wafer surface. The ion beam may be distributed over a semiconductor wafer surface area by beam scanning, by wafer movement, or by a combination of beam scanning and wafer movement. The ion beam may be a spot beam or a ribbon beam having long and short dimensions.
Carbon may be used as a co-implant species in association with another pre-amorphization implant (PAI) species, such as germanium, boron, etc. The idea is to position the carbon between a shallow dopant and end-of-range (EOR) damage caused by the PAI species. Substitutional carbon may block some interstitials coming back from EOR during an anneal process that may otherwise cause transient enhanced diffusion (TED) and boron interstitial cluster (BIC) formation. However, the position of carbon often overlaps with that of the PAI species, and so the carbon implant itself may contribute to PAI. Thus, carbon itself may also be used as a PAI species.
Carbon may also be used to create localized compressive strain. Therefore, if a source/drain in a transistor device is created from silicon carbon (SiC), carbon implantation may cause tensile strain in a channel of the transistor device. Incorporating carbon into a silicon lattice of the transistor device may require an epitaxial growth or a high implantation dose of carbon into the silicon lattice may cause amorphization. Also, carbon, in regrowth, may be incorporated into the silicon lattice and cause amorphization. As a result, amorphization and stress are both important factors considered by semiconductor manufacturers.
Accordingly, in view of the foregoing, it may be understood that there are significant problems and shortcomings associated with current technologies for ion implantation, and more particularly, for implanting molecular ions.